Russia is now in de facto military control of the Crimea region, despite Western condemnation of a “violation of Ukraine’s sovereignty”.

Ukraine has ordered full mobilisation to counter the military intervention.

Crimea is the main flashpoint, but there are also demonstrations in eastern Ukraine.

Some 2,000 people waving Russian flags gathered at the regional government building in Donesk to protest at the appointment of a new pro-Kiev governor.

Dozens later occupied the first floor of the building in Donesk, the hometown of ousted pro-Russian President Viktor Yanukovych.

Mr Lavrov said in Geneva on Monday that Russian troops were needed in Ukraine “until the normalisation of the political situation”.

Mr Lavrov said: “The victors intend to make use of the fruits of their victory to attack human rights and fundamental freedoms of minorities.”

He said the “violence of ultra-nationalists threatens the lives and the regional interests of Russians and the Russian speaking population”.

Mr Lavrov, who will meet UN Secretary General Ban Ki-moon in Geneva later, also condemned Western threats of sanctions and boycotts.

The BBC’s Imogen Foulkes, in Geneva, says the comments were in stark contrast to those in a text previously distributed to journalists, in which Mr Lavrov said that “military interventions on the pretext of civilian protection produce the opposite effect”.

In Kiev, Ukraine’s Prime Minister Arseniy Yatsenyuk said that any attempt to seize Crimea would fail.

However, he also said that “for today, no military options are on the table”, urging instead international economic and political support.

The crisis has hit Russian stock markets, with Moscow’s main MICEX index dropping 9% in early trading. The rouble fell to an all-time low against the US dollar and Russia’s central bank raised its key lending rate to 7% from 5.5%. World oil prices also surged.

The BBC’s Mark Lowen in Sevastopol says Crimea is now under de facto Russian armed control although no shots have been fired.

Two large Ukrainian military bases are surrounded and key installations like airports are occupied.